Touch screen panel for sensing touch using TFT photodetectors integrated thereon

ABSTRACT

A touch screen panel using a thin film transistor (TFT) photodetector includes a touch panel including a plurality of unit patterns for sensing light reflected by a touch by using a TFT photodetector including an active layer formed of amorphous silicon or polycrystalline silicon on an amorphous transparent material, and a controller configured to scan the plurality of unit patterns and read touch coordinates as a result of the scanning.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of application Ser. No. 16/824,071filed on Mar. 19, 2020, which claims priority to U.S. ProvisionalApplication No. 62/889,560 filed on Aug. 20, 2019. The aforementionedapplications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a touch screen panel which senses atouch through thin film transistor (TFT) photodetectors integratedthereon.

BACKGROUND

Technologies such as liquid crystals, organic light emitting diode(OLED) cells, touch screens, backlights, and thin film transistors(TFTs) on glass are integrated on a display panel. Particularly, thetrend of recent mobile devices is toward a display panel which tends tobe as large as or larger than an overall device size, and a displayitself is becoming more flexible.

However, the current display system performs only a one-way function ofoutputting an image or the like to the outside, without a function ofefficiently, directly acquiring an input signal. At present, the displaysystem executes only a touch screen function, with general performance.

A device for sensing a touch, such as a touch screen or a touch pad, isan input device attached to a display device to provide an intuitiveinput method to a user, and has been widely applied to variouselectronic devices such as a mobile phone, a navigation device, atablet, and the like. Particularly, as the demands for smartphonesincrease, more and more touch screens are adopted as touch sensingdevices which provide various input methods in a limited form factor.Along with this technological trend, the performance of touch screens isalso growing.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

An aspect of the disclosure is to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below.

Accordingly, an aspect of the disclosure is to implement ahigh-sensitivity touch panel on a glass substrate or a flexiblesubstrate such as a polyimide film, which is used as a touch screenpanel, by a thin film transistor (TFT) fabrication technology.

Another aspect of the disclosure is to recognize a touch fast andaccurately, using a touch screen panel having display pixels and a touchpanel integrated thereon.

Another aspect of the disclosure is to perform touch sensing without theneed for separately providing a light emitter for a touch panel, byusing a light emitting device or backlight unit (BLU) of a display as alight source for the touch panel.

Another aspect of the disclosure is to implement a transparent touchpanel capable of displaying and touch sensing by vertically stacking adisplay panel and a touch panel or arranging the display panel and thetouch panel on the same panel.

Another aspect of the disclosure is to fabricate a switching TFT fordisplay and a driving TFT for touch sensing in a single process byarranging a screen panel and a touch panel on the same panel.

Another aspect of the disclosure is to use a light source for a displayalso as a light source for a touch panel.

Another aspect of the disclosure is to use both of a BLU of a liquidcrystal display (LCD) and a light emitting source of an organic lightemitting diode (OLED).

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to an embodiment of the disclosure, a touch screen panel usinga TFT photodetector includes a touch panel including at least one unitpattern for sensing light reflected by a touch by using a TFTphotodetector including an active layer formed of amorphous silicon orpolycrystalline silicon on an amorphous transparent material, and acontroller configured to scan the at least one unit pattern and readtouch coordinates as a result of the scanning.

According to an embodiment of the disclosure, the touch panel mayinclude a plurality of first unit patterns which are arranged inparallel with each other in a first direction, and a plurality of secondunit patterns which are arranged in parallel with each other in a seconddirection crossing the first direction, insulated from the first unitpatterns.

According to an embodiment of the disclosure, the controller may beconfigured to scan each of the first unit patterns by supplying a firstvoltage to the plurality of first unit patterns line by line, scan allof the plurality of second unit patterns by sequentially supplying thefirst voltage to the plurality of second unit patterns according to afirst scanning control signal, each time each of the plurality of firstunit patterns is scanned, connect to the first and second unit patternsof the touch panel, and detect a touch recognition signal indicatingwhether a touch has occurred, and a touch position by comparing avoltage of initial capacitance of each unit pattern with a voltage ofcurrent capacitance of the unit pattern, each time the first voltage issupplied to the plurality of first unit patterns and the plurality ofsecond unit patterns by a driving circuit.

According to an embodiment of the disclosure, the controller may includea first driving circuit configured to scan the first unit patterns bysupplying the first voltage to the first unit patterns, and a seconddriving circuit configured to scan the second unit patterns by supplyingthe first voltage to the second unit patterns.

According to an embodiment of the disclosure, the first driving circuitmay include a plurality of first control switches configured torespectively supply the first voltage to the plurality of first unitpatterns in response to a first scanning control signal and a secondscanning signal from the controller, and a plurality of second controlswitches configured to respectively supply the first voltage to theplurality of second unit patterns in response to the first scanningcontrol signal and the second scanning signal from the controller.

According to an embodiment of the disclosure, the controller may includea first integration processor including a first capacitor charged by acapacitance variation in a unit pattern, a comparator configured tocompare a level of an output signal of the first integration processorwith a predetermined reference level, and a noise canceller including aplurality of switches operating according to an output of thecomparator. When the level of the output signal of the first integrationprocessor is higher than the reference level, the comparator may controleach of the plurality of switches to discharge the first capacitor.

According to an embodiment of the disclosure, the controller may furtherinclude a second integration processor including a second capacitorcharged by the charged first capacitor, and a calculator configured todetermine a touch input from an output signal of the second integrationprocessor.

According to an embodiment of the disclosure, the noise canceller mayinclude a first switch connected to a ground and a second switchconnected to an input node of the second integration processor. When thelevel of the output signal of the first integration processor is higherthan the reference level, the comparator may be configured to turn offthe second switch and turn on the first switch.

According to an embodiment of the disclosure, the comparator may includea first comparison circuit configured to compare the level of the outputsignal of the first integration processor with a first reference level,and a second comparison circuit configured to compare the level of theoutput signal of the first integration processor with a second referencelevel. When the level of the output signal of the first integrationprocessor is higher than the first reference level or lower than thesecond reference level, the comparator may operate each of the pluralityof switches to discharge the first capacitor.

According to an embodiment of the disclosure, the touch panel mayfurther include an infrared (IR) light source configured to causediffused reflection on the transparent material by irradiating IR lightfrom one side of the transparent material. The unit pattern may collectthe IR light diffusedly reflected from a body contacting the transparentmaterial, and the controller may process touch recognition along withpositioning of the body by the light generated from the IR light sourceand then collected.

According to an embodiment of the disclosure, the touch panel mayfurther include a backlight light source configured to irradiatebacklight in a transmission direction of the transparent materialthrough a space between adjacent TFT photodetectors. The unit patternmay collect the backlight passed through the transparent material andthen reflected back from the body, and the controller may process touchrecognition along with the positioning of the body by the lightgenerated from the backlight light source and then collected.

According to an embodiment of the disclosure, the unit pattern mayinclude the TFT photodetector including the active layer formed ofamorphous silicon or polycrystalline silicon on an amorphous transparentsubstrate, and at least one transistor electrically coupled to the TFTphotodetector and configured to generate a voltage output fromphotocurrent generated in the active layer.

According to an embodiment of the disclosure, the TFT photodetector maybe formed in a structure in which when light is incident, electronsmigrate into an N-type gate by tunneling from a P-type active layer toan oxide film, among charges of two PN areas excited with the oxide filmin between, the electron migration changes a threshold voltage of acurrent channel between a source and a drain in correspondence with achange in a total amount of charge in the gate, photocurrentproportional to the intensity of the incident light flows in the activelayer, and a voltage output is generated from the flowing photocurrent.

According to an embodiment of the disclosure, the active layer mayinclude a material having a conductive property controllable bytunneling or an electric field.

According to an embodiment of the disclosure, the active layer mayinclude at least one of amorphous silicon or polycrystalline silicon.

According to an embodiment of the disclosure, the TFT photodetector mayinclude an amorphous transparent substrate including the transparentmaterial, a source formed of amorphous silicon or polycrystallinesilicon on the transparent substrate, a drain formed of amorphoussilicon or polycrystalline silicon, opposite to the source on thetransparent substrate, the active layer formed between the source andthe drain and including a current channel formed between the source andthe drain, an insulating oxide film formed on the source, the drain, andthe active layer, and a light receiver formed on the insulating oxidefilm, configured to absorb light, and insulated from the active layer bythe insulating oxide film.

According to an embodiment of the disclosure, in the TFT photodetector,when light is incident on the light receiver, electrons may migrate bytunneling through the insulating oxide film between the light receiverand the active layer excited with the insulating oxide film in between,the electron migration may change an amount of charge in the lightreceiver, the changed amount of charge may change a threshold voltage ofthe current channel, and thus photocurrent may flow in the currentchannel.

According to an embodiment of the disclosure, the TFT photodetector mayuse light generated from a display panel as a light source for the unitpattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic diagram illustrating a display module used as atouch panel in an electronic device with thin film transistor (TFT)photodetectors implemented on the touch panel according to an embodimentof the disclosure;

FIG. 2 is a diagram illustrating an exemplary TFT photodetectorimplemented on a pixel basis on a display according to an embodiment ofthe disclosure;

FIGS. 3A and 3B are sectional views illustrating exemplaryimplementations of a TFT photodetector on a pixel basis on a displayaccording to an embodiment of the disclosure;

FIG. 4 is a sectional view illustrating a TFT photodetector according toan embodiment of the disclosure;

FIGS. 5A-5D are sectional views illustrating a process of fabricating aTFT photodetector according to an embodiment of the disclosure;

FIG. 6 is an energy band diagram illustrating a photo-electricconversion mechanism of a TFT photodetector according to an embodimentof the disclosure;

FIG. 7 is an energy band diagram illustrating a tunneling mechanism of aTFT photodetector according to an embodiment of the disclosure;

FIG. 8 is a diagram illustrating a photo-electric conversion mechanismcaused by a plurality of localized states in a TFT photodetector formedof amorphous silicon (a-Si) or polycrystalline silicon (poly-Si orP-Si);

FIGS. 9 and 10 are diagrams illustrating unit patterns (or unit pixels)when an active layer is 100 nm or less thick;

FIGS. 11 and 12 are diagrams illustrating unit patterns (or unit pixels)when an active layer is 100 nm or more thick;

FIG. 13 is a diagram illustrating a touch screen panel according to anembodiment of the disclosure;

FIG. 14 is a diagram illustrating a touch screen panel according toanother embodiment of the disclosure;

FIG. 15 is a block diagram of a controller according to an embodiment ofthe disclosure;

FIG. 16 is a diagram illustrating a touch panel which processes touchrecognition by using an infrared (IR) light source; and

FIG. 17 is a diagram illustrating a touch panel which processes touchrecognition by using a backlight light source.

DETAILED DESCRIPTION

The disclosure will be described in detail with reference to theattached drawings. Lest it should obscure the subject matter of thedisclosure, a known technology will not be described in detail. Anordinal number (e.g., first, second, and so on) used in the descriptionof the disclosure is used simply to distinguish one component fromanother component.

When it is said that one component is “coupled to or with” or “connectedto” another component, it is to be understood that the one component maybe coupled to or connected to the other component directly or with athird party in between.

FIG. 1 is a schematic diagram illustrating a display module used as atouch panel in an electronic device with thin film transistor (TFT)photodetectors implemented on the touch panel according to an embodimentof the disclosure.

A TFT photodetector 100 according to the disclosure is formed on a touchscreen panel 200 in an electronic device 10. The electronic device 10may be any device equipped with a display, such as a smartphone, alaptop computer, a monitor, or a TV.

Specifically, TFT photodetectors 100 may be formed across the whole orpart of the touch screen panel 200, and a TFT photodetector 100 may beformed in each individual pixel, thus operating as a part of the pixel.When TFT photodetectors 100 are formed across the whole touch screenpanel 200, the number of the TFT photodetectors 100 may be equal to thenumber of pixels corresponding to the resolution of the touch screenpanel 200. The touch screen panel 200 may be any of a light receivingdisplay requiring a backlight unit (BLU), such as a liquid crystaldisplay (LCD) or a light emitting display which emits light on its own,such as a light emitting diode (LED) (e.g., organic LED (OLED) or activematrix OLED (AMOLED)) display or a plasma display panel (PDP).

The touch screen panel 200 displays a video or an image or operates as atouch panel, according to an operation of the electronic device 10. Whenthe touch screen panel 200 operates as a touch panel, an optical imageof an external object may be acquired by means of a plurality of TFTphotodetectors 100 implemented on the touch screen panel 200. A lightsource required for touch sensing may be an external light source suchas natural light or an external lighting, or an internal light sourcesuch as a BLU or OLED elements of the touch screen panel 200.

As such, formation of TFT photodetectors 100 according to the disclosureon the touch screen panel 200 advantageously enables use of the touchscreen panel 200 as a touch panel without the need for providing aseparate touch panel in the electronic device 10. Further, because thetouch screen panel 200 is used as a touch panel, a light source fordisplay may also be used as a light source for touch sensing without theneed for adding a light source for touch sensing in the electronicdevice 10. Therefore, the effects of device simplification and reducedfabrication cost may be expected.

Further, because a pixel of a unit pattern is formed in the same size aseach pixel of the display, as many unit patterns as the number of pixelscorresponding to the resolution of the display may be arranged in theelectronic device 10. In this case, the whole display may serve as atouch panel. The electronic device 10 may acquire an image of anexternal object by controlling the touch panel in the whole or part ofthe display. Hereinbelow, the term “touch panel” is interchangeably usedwith “unit patterns of the touch panel”. Obviously, a TFT photodetector100 of the disclosure is formed in a unit pattern of the touch panel. Aunit pattern will be described in detail with reference to FIG. 9.

Further, the electronic device 10 may acquire biometric informationabout an external object, such as information about a fingerprint, thevein of a finger, a face, or an iris, by the touch screen panel 200 withthe TFT photodetectors 100 implemented thereon. For example, a user mayenable acquisition of a fingerprint image through a plurality of imagesensor pixels formed on an area of the display by touching the area witha finger or placing a finger within a predetermined distance to the areain the electronic device 10. Throughout the specification, the touchscreen panel 200 may also be referred to as a display panel or a displayin the same sense.

Now, a description will be given of implementation of TFT photodetectorson a touch panel.

FIG. 2 is a diagram illustrating exemplary implementation of a TFTphotodetector in each pixel of a display according to an embodiment ofthe disclosure.

Although the TFT photodetector 100 operates in a similar principle tothat of a photo assisted tunneling-photodetector (PAT-PD) disclosed inU.S. patent application Ser. No. 15/885,757, the TFT photodetector 100and the PAT-PD are different in that the PAT-PD is formed on a singlecrystalline silicon substrate, and an active layer, a source, a drain,and a gate serving as a light receiver are formed of single crystallinesilicon, whereas the TFT photodetector 100 of the disclosure is formedon the touch screen panel 200 which is a glass substrate or atransparent flexible substrate using a transparent film formed of, forexample, polyimide (PI), polyethylene terephthalate (PET), polypropylene(PP), polycarbonate (PC), polymethylmethacrylate (PMMA),polyethylenenaphthalate (PEN), polyetheretherketone (PEEK),polyethersulfone (PES), or polyarylite, and an active layer, a source, adrain, and a light receiver are formed of amorphous silicon (a-Si) orpolycrystalline silicon (poly-Si or P-Si). Glass or a PI film isamorphous, which makes it impossible to stack single crystalline siliconthereon. Therefore, when TFT photodetectors are formed on a glasssubstrate or a flexible substrate, the TFT photodetectors should beamorphous or polycrystalline. Under circumstances, the amorphous siliconor the polycrystalline silicon may be replaced with a material with aconductive property controllable by an electric field or tunneling.Throughout the specification, the term “PAT-PD” or “TFT PAT-PD” isinterchangeably used with “TFT photodetector”.

Preferably, display pixels and touch panels are matched to each other ina one-to-one correspondence. FIG. 2 illustrates an exemplary pixelstructure on the touch screen panel 200 with TFT photodetectors 100implemented thereon. A unit pattern 300 of the touch screen panel 200includes a light emitting area 310 for display, a driving switch 320,and a TFT photodetector 100 for touch sensing. The touch screen panel200 may be designed such that the area of a unit pattern on a touchpanel and the area of each pixel of the touch panel are of similar sizesand thus the display pixels and the touch panels are matched in aone-to-one correspondence per position. In this case, as the TFTphotodetector 100 may operate using the light emitting area 310 of thedisplay pixel as a light source, a signal may be processed by matchingthe light emitting area 310 to the TFT photodetector 100, and data maybe processed by matching data included in the light source to datacollected by the TFT photodetector 100.

Although it is preferable to form the TFT photodetector 100 without anyoverlap with the light emitting area 310, the TFT photodetector 100 maybe formed overlapping with the light emitting area 310 over apredetermined area because the TFT photodetector 100 occupies a smallarea relative to the light emitting area 310. However, to maximize aphotoelectric conversion effect, the introduction of unnecessary lightis blocked by shielding an area except for the light receiver of the TFTphotodetector 100 with a metal or the like. The resulting shielding of apart of the light emitting area 310 with the light shielding area exceptfor the light receiver of the TFT photodetector 100 may decrease thelight emission efficiency of the display.

In some cases, the display pixels and the touch panels may be configuredin different sizes. For example, when the unit pixels of the imagesensor are designed such that one display pixel area corresponds to ntouch panels, n TFT photodetectors 100 share the light emitting area ofone display pixel as a light source, making it difficult to control theTFT photodetectors 100 individually by light source control. However,the light source control may be simplified, which in turn simplifies atouch sensing process. On the contrary, the touch panels may be designedsuch that the area of a touch panel corresponds to the area of m displaypixels. In this case, although fewer touch panels than the number ofpixels corresponding to the resolution of the display may be arranged,one TFT photodetector 100 uses the light emitting areas of m displaypixels as a light source, and thus fine light source control and dataprocessing required for touch sensing may become difficult.

The light emitting area 310 may be formed in a different structureaccording to the type of a used display. For example, when the touchscreen panel 200 of the electronic device 10 is a light emitting displaysuch as an OLED display, the light emitting area 310 may be a lightemitting pixel with red, green, blue (RGB) sub-pixels arranged therein.When the touch screen panel 200 of the electronic device 10 is a lightreceiving display such as an LCD, RGB sub-filters may be arranged in thelight emitting area 310. Obviously, the TFT photodetector 100 may use anexternal light source such as natural light as a light source for touchsensing, instead of the light emitting area 310.

With reference made to FIG. 2 again, a plurality of unit patterns 300are arranged in a lattice structure on the touch screen panel 200. Eachunit pattern 300 may be formed by vertically stacking or arranging sideby side a display sub-panel formed on a glass substrate or a transparentflexible substrate and a touch sub-panel formed on a glass substrate ora transparent flexible substrate. In this regard, FIGS. 3A and 3Billustrate the cross sections of unit patterns 300 on the display.

Referring to FIGS. 3A and 3B, the unit pattern 300 of a touch panelincludes a display sub-panel 330 and a touch sub-panel 340. The displaysub-panel 330 may include a light emitting area 310 for display and itsdriving switch 320, and the touch sub-panel 340 may include a TFTphotodetector 100 for touch sensing and a detector driving TFT 344 fordriving the TFT photodetector 100.

For example, the detector driving TFT 344 may include at least onetransistor which is electrically coupled to a source side of the TFTphotodetector 100 and generates a voltage output from photocurrentgenerated in the active layer of the TFT photodetector 100.

The display sub-panel 330 or the touch sub-panel 340 is formed on atransparent glass substrate or a transparent flexible substrate such asa PI film (hereinafter, also referred to as a glass substrate or atransparent substrate). The transparent touch screen panel 200 may beformed by vertically stacking and attaching the two panels asillustrated in FIG. 3A or arranging the two panels side by side on thesame glass substrate 334 as illustrated in FIG. 3B.

Particularly, the touch sub-panel 340 may be stacked with the displaysub-panel 330 in the structure of FIG. 3A. Further, in reaction to lightsensed by the touch sub-panel 340, a voltage output may be generatedfrom photocurrent generated from the active layer.

When light is incident on the touch sub-panel 340, electrons areintroduced into an N-type gate by tunneling from a P-type active layerto an oxide film, among charges of two PN areas excited with the oxidefilm in between. The electron migration changes the threshold voltage ofa current channel between a source and a drain in correspondence with achange in the total amount of charge in the gate, and thus photocurrentproportional to the intensity of the incident light flows in the activelayer. Further, the touch sub-panel 340 may generate a voltage outputfrom the flowing photocurrent.

Alternatively, the light emitting area 310 and the driving switch 320 ofan OLED device for display, and the TFT photodetector 100 for touchsensing and the detector driving TFT 344 may be arranged together on thesame glass substrate 332 or 342, as illustrated in FIG. 3B. In thiscase, a driving switch 322 may be formed by incorporating a switchingTFT for controlling the light emitting area 310 with a switching TFT forcontrolling the TFT photodetector 100, or driving switches may be formedseparately.

Throughout the specification, the display sub-panel 330 and the touchsub-panel 340 may also be referred to as a display pixel and a touchpanel, respectively.

As described before, the image sensor pixel 340 of a similar size tothat of the display pixel 330 senses light and acquires an image bysignal processing and detector driving, and includes the TFTphotodetector 100 and the detector driving TFT 344 for driving the TFTphotodetector 100. The driving switch 320 for an output to be used fordisplay, and the detector driving TFT 344 for driving the TFTphotodetector 100 formed on a touch panel basis may be integrated orconfigured separately. In this manner, the TFT photodetector 100 of thedisclosure is formed on a pixel basis.

Because the TFT photodetector 100 should be formed on an amorphoussubstrate such as a glass substrate or a PI film, not a singlecrystalline silicon substrate, the TFT photodetector 100 should beimplemented in a different manner from an existing photodetector usingsingle crystalline silicon. Now, a description will be given of adetailed structure, operation mechanism, fabrication method of a TFTphotodetector according to the disclosure.

FIG. 4 is a sectional view illustrating a TFT photodetector according toan embodiment of the disclosure.

Referring to FIG. 4, the TFT photodetector 100 of the disclosure isformed on the transparent substrate 342 such as an amorphous glasssubstrate or a flexible substrate, and includes, on the transparentsubstrate 342, a gate 150 formed of a-Si or poly-Si, an insulating oxidefilm 140 capable of controlling tunneling of optically excited charges,a drain 110, a source 120, and an active layer 130 in which a currentchannel is formed between the source 120 and the drain 110. While thedrain 110, the source 120, the active layer 130, and the gate 150 areformed of a-Si or poly-Si, they may be formed of any other material asfar as the material has a conductive property controllable by tunnelingor an electric field.

The gate 150 is formed of N-type poly-Si or a-Si by implanting an N-typeimpurity and operates as a light receiver that absorbs incident light.The active layer 130 is formed of P-type poly-Si or a-Si, with theinsulating oxide film 140 between the active layer 130 and the gate 150.The active layer 130 forms a current channel according to opticalexcitation between the drain 110 and the source 120 which are P+-typediffusion layers.

An area on which light is incident is confined to the gate 150 servingas the light receiver and the active layer 130 with the insulating oxidefilm 140 interposed between the active layer 130 and the gate 150. Forthis purpose, a metal protection layer 160 may be formed on a boundarysurface of the transparent substrate 342, except for the area betweenthe transparent substrate 342 and the active layer 130, to shieldunnecessary light introduced into the TFT photodetector 100. A metalshielding layer 170 may be formed in the remaining area except for thegate 150 in an upper part of the TFT photodetector 100. The shieldinglayer 170 may be formed by a silicide and metal process. The TFTphotodetector 100 limits an area on which light is incident to the gate150 serving as the light receiver by means of the shielding layer 170,thereby maximizing the photoelectric conversion in the gate 150.Hereinbelow, the gate 150 and the light receiver are interchangeablyused throughout the specification.

With no light introduced, the TFT photodetector 100 controls biases ofthe gate 150, the drain 110, the source 120, and the active layer 130 tomaintain a stable equilibrium state in which electrons are trapped. Forthis purpose, the overlying shielding layer 170 and the metal protectionlayer 160 on the boundary surface of the transparent substrate 342 areprovided to shield unintended unnecessary light through the transparentsubstrate 342 of, for example, glass. Specifically, the active layer 130between the source 120 and the drain 110 is bias-controlled to have athreshold voltage at which the potential state of a silicon surface onwhich a current channel may be formed is shortly before a sub-thresholdstate during an initial fabrication process. In this state, when lightis not incident on the gate 150 as the light receiver, photocurrent doesnot flow in the current channel.

When light is incident on the light receiver, electrons are introducedinto the N-type gate 150 by tunneling from the P-type active layer 130to the insulating oxide film 140, among charges of the two PN areasexcited with the insulating oxide layer 140 in between, the electronmigration changes the threshold voltage of the current channel betweenthe source 120 and the drain 110 in correspondence with a change in thetotal amount of charge in the gate 150, the threshold voltage modulationeffect caused by the change in the amount of charge in the lightreceiver causes a change in the conductance of the current channel, andthus photocurrent corresponding to the changed conductance flows.

Since the gate 150 is doped with holes, the electrons passed through theinsulating oxide film 140 by tunneling are combined with holes in anarea of the gate 150 near to the insulating oxide film 140, therebygenerating a depletion layer at the top end of the insulating oxide film140. Therefore, the threshold voltage drops due to a change in thecharge of the active layer 130 near to the insulating oxide film 140,thereby exciting the current channel between the source 120 and thedrain 110.

In other words, current that flows in the current channel excitedbetween the source 120 and the drain 110 by light reception at the lightreceiver is not a direct flow of charges of electron-hole pairs (EHPs)caused by the light reception but an indirect current flow in thecurrent channel excited by tunneling of directly generated charges.Therefore, a very high-efficiency light detection capability may beachieved.

FIGS. 5A-5D are sectional views illustrating a process of fabricating aTFT photodetector according to an embodiment of the disclosure.

In FIG. 5A, the P-type poly-Si or a-Si diffusion layer 130 to be used asan active layer is formed on the glass substrate 342 or a flexiblesubstrate of, for example, a PI film, and two P+-type diffusion layers111 and 121 are formed of a-Si or poly-Si at both sides of the diffusionlayer 130.

The diffusion layers 130, 111, and 121 may be formed of a-Si or poly-Si.To increase mobility, the diffusion layers 130, 111, and 121 may beformed by depositing a-Si and then crystalizing the deposited a-Si intopoly crystals by thermal treatment such as laser annealing, or directlydepositing poly-Si on the transparent substrate.

Subsequently, a thin SiO₂ or SiNx insulating oxide film 141 is formed onthe diffusion layers 130, 111, and 121. The insulating oxide film 141may be formed by sputtering or plasma enhanced chemical vapor deposition(PECVD).

Subsequently, an N-type diffusion layer 151 is formed of poly-SI or a-Sion the insulating oxide film 141 in the same manner.

Referring to FIG. 5B, the gate 150 is then formed for use as a lightreceiver by photo-patterning the generated diffusion layer 151.Referring to FIG. 5C, the generated insulating oxide layer 141 is etchedaway, remaining only a necessary part by a photoresist (PR) patterningprocess. Partial insulating oxide films 142 and 143 are removed togetheron areas of the diffusion layer 121, which are to be used as the source120 and the drain 110, so that a source electrode and a drain electrodemay be connected.

Referring to FIG. 5D, the remaining area except for the areas to be usedas the source 120 and the drain 110 is then removed from the P+-typediffusion layers 111 and 121 by etching. Electrodes are formed bydepositing a metal or the like in the areas of the insulating oxidefilms 142 and 143 which have been removed in the source 120 and thedrain 110.

In the TFT photodetector 100 fabricated in the above manner, currentflows through a current channel excited between the source 120 and thedrain 110 by tunneling, as described before. If the thickness of theactive layer 130 is equal to or larger than a predetermined thickness,for example, 100 nm, a neutral area is produced separately in an areaunder the gate 150, which has not been depleted perfectly, aside fromthe current channel generated by light. Unnecessary extra chargesgenerated by light may be accumulated in the neutral area, and arelikely to act as a changing factor to the threshold voltage whichlinearly changes by light. Therefore, the neutral area needs separateprocessing.

FIG. 6 is an energy band diagram referred to for describing aphotoelectric conversion mechanism of a TFT photodetector according toan embodiment of the disclosure.

When light is incident on the gate 150 as the light receiver, EHPs aregenerated in the gate 150 and the active layer 130. Excited electrons ofthe active layer 130 tunnels through the insulating oxide film 140 by anelectric field, thereby depleting a bottom end portion of the gate 150.As a result, the total charge amount of the gate 150 is changed, whichleads to a threshold voltage modulation effect equivalent to applicationof a negative power source to the gate 150. Accordingly, a currentchannel is formed in the active layer 130 of poly-Si, and thus currentflows between the source 120 and the drain 110. The TFT photodetector100 implemented based on this structure and principle has ahigh-sensitivity detection capability of sensing even a single photonand enables very intense photocurrent to flow even with a small amountof light.

FIG. 7 is an energy band diagram referred to for describing a tunnelingmechanism of a TFT photodetector according to an embodiment of thedisclosure.

In the TFT photodetector 100, the shielding layer 170 is formed suchthat only the gate 150 serving as the light receiver and the activelayer 130 facing the gate 150 with the insulating oxide film 140 inbetween are affected by light, with no effect of light on the remainingarea. The shielding layer 170 may be formed by a silicide and metalprocess, and may not be formed on the gate 150 through a mask.

Light of multiple wavelengths incident on the TFT photodetector 100 ismostly transmitted through or absorbed to the gate 150 formed of poly-Sior a-Si.

If the thickness of the gate 150 is equal to or larger than apredetermined value, for example, 300 nm, short-wavelength light of theblue family in light incident on the TFT photodetector 100 is mostlyabsorbed to the gate 150, while only very partial short-wavelength lightreaches the active layer 130 under the gate 150.

As described above, since the TFT photodetector 100 has an excellenthigh-sensitivity detection capability compared to a conventionalphotodetector, even though only a very small part of light of a shortwavelength incident on the gate 150 is transmitted through the gate 150and reaches the active layer 130, the threshold voltage of the currentchannel is accordingly changed and thus even a slight change in lightmay be sensed.

Light of the other wavelengths is also transmitted through the gate 150and reaches the active layer 130 in the same principle. Accordingly, thesame phenomenon as observed from reception of light of a shortwavelength occurs to the gate 150, thereby causing a change in thethreshold voltage of the current channel. However, because light of arelatively long wavelength is easily transmitted through the gate 150and reaches the active layer 130, compared to light of a shortwavelength, the light of a long wavelength generates more EHPs in theactive layer 130. Therefore, more electrons migrate to the gate 150through the insulating oxide film 140 by tunneling, causing a change inthe threshold voltage of the current channel between the source 120 andthe drain 110.

The metal protection layer 160 formed between the transparent substrate342 and the active layer 130 blocks light introduced through thetransparent substrate 342 from reaching an area other than the activelayer 130. Therefore, the light is absorbed only to or transmitted onlythrough the active layer 130 adjacent to the gate 150, leading toefficient tunneling through the insulating oxide film 140.

For more efficient tunneling, a predetermined voltage may be appliedbetween the gate 150 of poly-Si and the active layer 130 of poly-Si, ora property such as dark current may be adjusted by adjusting a tunnelingprobability and controlling an initial threshold voltage of the TFTphotodetector 100.

Then, when the intensity of light is decreased or light is blocked,tunneled electrons are re-tunneled to the active layer 130, and thus theamount of charge in the gate 150 returns to an original level.Accordingly, the formed depletion layer is reduced and, at the sametime, photocurrent generated in the current channel is also reduced.

However, it may occur that charges have not completely disappeared andthus have remained in the active layer 130 even after the lightblocking, causing an error such as a signal delay in the next lightirradiation. To avert this problem, the thickness of the active layer130 may be controlled such that an area remaining as a neutral area, inwhich no channel is generated, may be reduced, or a reset device may beadded to remove the charges remaining in the active layer 130.

FIG. 8 illustrates a mechanism for photoelectric conversion caused by aplurality of localized states in a TFT photodetector formed of a-Si orpoly-Si.

Panel (a) of FIG. 8 illustrates the energy band of general singlecrystalline silicon, and panel (b) of FIG. 8 illustrates the energybands of the gate and the active layer of a TFT photodetector of a-Si orpoly-Si.

In the TFT photodetector 100, electrons are introduced into the N-typegate 150 by tunneling from the P-type active layer 130 to the insulatingoxide film 140, among charges of the two PN areas excited with theinsulating oxide layer 140 in between, the electron migration changesthe threshold voltage of the current channel between the source 120 andthe drain 110 in correspondence with a change in the total amount ofcharge in the gate 150, the threshold voltage modulation effect causedby the change in the amount of charge in the light receiver causes achange in the conductance of the current channel, and thus photocurrentcorresponding to the changed conductance flows.

As the gate 150 as the light receiver and the active layer 130 areformed of a-Si or poly-Si, instead of single crystalline silicon,according to an embodiment of the disclosure, a plurality of localizedenergy levels are formed in the gate 150 and the active layer 130,thereby forming a wavelength extension layer 180 that extends thewavelength range of light absorbed by the TFT photodetector 100.

The wavelength extension layer 180 is formed of a-Si or poly-Si. Asillustrated in panel (b) of FIG. 8, a plurality of local energy levelsare generated through multiple localized states formed in a forbiddenband between the conduction band and valence band of the gate 150 andthe active layer 130. The localized states are naturally generated inthe forbidden band in view of the nature of the a-Si/poly-Si structure,which obviates the need for applying stress or implanting ion toartificially form the localized states. Therefore, processes aresimplified.

Accordingly, the TFT photodetector 100 may generate EHPs by absorbinglight even at an energy level lower than 1.12 eV which is the band gapenergy of the general single crystalline silicon, thereby enablingdetection of the wavelength range of the near-infrared area, which islonger than a maximum detectable wavelength of silicon, 1150 nm, anddetection of light in a wavelength that a general silicon photodiode isnot capable of detecting.

As described above, because the TFT photodetector 100 is formed of a-Sior poly-Si, compared to a conventional photodetector formed of singlecrystalline silicon, the wavelength extension layer 180 includingmultiple localized states in the forbidden band exists, and there is noneed for artificially forming localized states by applying uniaxialtensile stress on single crystalline silicon, combining hetero elements(e.g., Ge or the like), implanting ions (e.g., P, B, N, Ga, or thelike), or increasing the doping density of an oxide film, poly-Si,and/or a substrate to control a thermal process strength. Therefore, afabrication process is simplified.

As described before, the TFT photodetector 100 according to theembodiment of the disclosure may generate a flow of photocurrent with anintensity higher than the conventional photodetector by hundreds oftimes to a few thousands of times, for the same light intensity.

Further, because the TFT photodetector 100 according to the embodimentof the disclosure includes a plurality of localized states, thewavelength range in which a valid signal is detectable is extended.Thus, the TFT photodetector 100 is applicable to a sensor for touchrecognition, or the like.

While the TFT photodetector 100 has been described as implemented in asimilar structure to a P-channel metal-oxide semiconductor (PMOS), thisshould not be construed as limiting. The TFT photodetector 100 may beimplemented in a similar structure to an N-channel metal-oxidesemiconductor (NMOS) by exchanging the doping impurities of the gate andthe active layer.

With reference to FIGS. 9 to 14, a unit pattern including a TFTphotodetector 100 will be described in greater detail.

When a PAT-PD pixel is formed on a substrate by the above-described TFTprocess, various types of pixel structures are available according tothe thickness of an active layer.

The substrate may include a glass substrate or a flexible substrate suchas a polyimide film.

The active layer may include a material with a conductive propertycontrollable by tunneling or an electric field. For example, the activelayer may include at least one of a-Si or poly-Si.

According to the disclosure, a transparent touch screen panel capable ofdisplaying and touch sensing may be implemented by vertically stacking adisplay panel and a touch panel or arranging the display panel and thetouch panel on the same panel.

Further, according to the disclosure, a switching TFT for display and adriving TFT for touch sensing may be fabricated in a single process byarranging a screen panel and a touch panel on the same panel.

Embodiments of the pixel structure of a unit pattern according to thethickness of an active layer will be described with reference to FIGS. 9to 12.

The active layer may have a different pixel structure according to areference value, for example, a thickness of 100 nm.

FIGS. 9 and 10 are diagrams illustrating unit patterns when an activelayer is 100 nm or less thick.

A unit pattern 910 may include a TFT photodetector 911 having an activelayer formed of a-Si or poly-Si and at least one transistor on anamorphous transparent substrate. In the embodiment of FIG. 9, the atleast one transistor may include transistors M1, M2 and M3.

In the TFT photodetector 911, when light is incident, electrons may beintroduced into an N-type gate by tunneling from a P-type active layerto an oxide film, among charges of two PN areas excited with the oxidelayer in between. As the introduced electron migrate, a thresholdvoltage of a current channel between a source and a drain is changed incorrespondence with a change in the total amount of charge in the gate.Further, photocurrent proportional to the intensity of the incidentlight flows in the TFT photodetector 911 according to the changedthreshold voltage. The TFT photodetector 911 may generate a voltageoutput from the flowing photocurrent. The transistors M1, M2 and M3 maybe electrically coupled to the TFT photodetector 911 and generate avoltage output from photocurrent generated in the active layer of theTFT photodetector 911.

In FIG. 9, the unit pattern 910 may convert photocurrent into a voltageoutput using parasitic capacitance generated in at least one transistor.

Specifically, the unit pattern 910 may be convert photocurrent into avoltage output using parasitic capacitance generated between thetransistors M1 and M3.

The transistor M2, which is a selection transistor, may control chargingof a parasitic capacitor.

Specifically, when the selection transistor M2 is turned on,photocurrent obtained by photo-electric conversion in the TFTphotodetector 911 may be charged in the parasitic capacitor. Further,the photocurrent charged in the parasitic capacitor may be realized asan image.

In the turn-on state, the selection transistor M2 may reset signals whenBUS RST is turned on.

Specifically, when BUS RST is turned on in the turn-on state of thetransistor M2, charges may be removed from an entire column bus and theTFT photodetector 911 through a ground GND.

In this operation, an integration time substantially required for atouch sensor may be defined, and a continuous touch may be obtained in ashutter scheme.

FIG. 10 illustrates a unit pattern 1010 which directly charges acapacitor, instead of parasitic capacitance.

Specifically, the unit pattern 1010 may directly charge a capacitor 1012coupled to a source follower with photocurrent generated from a TFTphotodetector 1011 in response to a touch.

In the TFT photodetector 1011, when light is incident, electrons may beintroduced into an N-type gate by tunneling from a P-type active layerto an oxide film, among charges of two PN areas excited with the oxidelayer in between. As the introduced electron migrate, a thresholdvoltage of a current channel between a source and a drain is changed incorrespondence with a change in the total amount of charge in the gate.Further, photocurrent proportional to the intensity of the incidentlight flows in the TFT photodetector 1011 according to the changedthreshold voltage. The TFT photodetector 1011 may generate a voltageoutput from the flowing photocurrent. Transistors M1, M2 and M3 may beelectrically coupled to the TFT photodetector 1011 and generate avoltage output from photocurrent generated in the active layer of theTFT photodetector 1011.

In the embodiment of FIG. 10, the use of the capacitor 1012 may lead tolarger capacitance than parasitic capacitance. Further, the largecapacitance may be controlled to obtain a larger dynamic-range outputcharacteristic than in the embodiment of FIG. 9.

In the embodiment of FIG. 10, at least one transistor may include aselection transistor M1.

When the selection transistor M1 is turned on, the capacitor 1012 of anIVC circuit may be charged, among capacitors coupled to a transistorcorresponding to a source follower.

Specifically, photocurrent obtained by photo-electric conversion in theTFT photodetector 1011 may be charged in the capacitor 1012 of the IVCcircuit inside a pixel due to the turn-on of the selection transistorM1.

Further, the photocurrent charged in the capacitor 1012 may be convertedinto a voltage and output as IVC_OUT, which may be delivered in the formof a signal to a separate driving circuit such as co-double sampling(CDS).

The transmitted signal may be reset by the selection transistor M1.

For example, when BUS RST (M2) is turned on in the turn-on state of theselection transistor M1, charges may be removed from the capacitor 1012,an entire column bus, and the TFT photodetector 1011 of the IVC circuitthrough a ground GND.

In this operation, an integration time substantially required for atouch sensor may be defined, and successive images may be obtained in ashutter scheme.

For example, because an active layer of poly-Si may be formed to athickness smaller than 100 nm on glass in the TFT photodetector 1011used in FIG. 10, a fully depleted current channel area may be achieved.

Further, since the fully depleted current channel area may be formed inthe TFT photodetector 1011 in FIG. 10, a detector transistor for resetis not required separately.

FIGS. 11 and 12 are diagrams illustrating unit patterns when an activelayer is 100 nm or more thick.

When a poly-Si active layer is formed to a thickness of 100 nm or moreon glass in a fabrication process, a neutral area is formed under a gatewhich has not been fully depleted in addition to a current channelgenerated by light.

Unnecessary extra charges generated by light may be accumulated in thisneutral area. Moreover, the accumulated charges may act as a separatefactor that changes a threshold voltage which linearly changes by light.

The residual charges may be controlled by directly coupling anadditional transistor to the active layer.

Referring to FIG. 11, for this purpose, a unit pattern 1110 includes aTFT photodetector 1111 having a poly-Si active layer formed to athickness of 100 nm or more.

In the TFT photodetector 1111, when light is incident in response to atouch, electrons may be introduced into an N-type gate by tunneling froma P-type active layer to an oxide film, among charges of two PN areasexcited with the oxide layer in between. As the introduced electronmigrate, a threshold voltage of a current channel between a source and adrain is changed in correspondence with a change in the total amount ofcharge in the gate. Further, photocurrent proportional to the intensityof the incident light flows in the TFT photodetector 1111 according tothe changed threshold voltage. The TFT photodetector 1111 may generate avoltage output from the flowing photocurrent. Transistors M1 and M2 maybe electrically coupled to the TFT photodetector 1111 and generate avoltage output from photocurrent generated in the active layer of theTFT photodetector 1111.

A transistor M3 is directly coupled to the active layer of the TFTphotodetector 1111.

The transistor M3 may be configured to have a gate connected to VDD, adrain connected to the active layer of the TFT photodetector 1111, and asource connected to SCG. That is, as VDD is input to the gate,unnecessary extra residual charges accumulated in the poly-Si activelayer of the TFT photodetector 1111 may flow from the drain to thesource to be controlled through an SCG channel.

Referring to FIG. 12, a unit pattern 1210 includes a TFT photodetector1211 having a poly-Si active layer formed to a thickness of 100 nm ormore.

In the TFT photodetector 1211, when light is incident in response to atouch, electrons may be introduced into an N-type gate by tunneling froma P-type active layer to an oxide film, among charges of two PN areasexcited with the oxide layer in between. As the introduced electronmigrate, a threshold voltage of a current channel between a source and adrain is changed in correspondence with a change in the total amount ofcharge in the gate. Further, photocurrent proportional to the intensityof the incident light flows in the TFT photodetector 1211 according tothe changed threshold voltage. The TFT photodetector 1211 may generate avoltage output from the flowing photocurrent. Transistors M1, M2 and M3may be electrically coupled to the TFT photodetector 1211 and generate avoltage output from photocurrent generated in the active layer of theTFT photodetector 1211.

A transistor M4 is directly coupled to the active layer of the TFTphotodetector 1211.

The transistor M4 may be configured to have a gate connected to RST, adrain connected to the active layer of the TFT photodetector 1211, and asource connected to RST. That is, as RST is input to the gate,unnecessary extra residual charges accumulated in the poly-Si activelayer of the TFT photodetector 1211 may flow from the drain to thesource, for reset.

FIG. 12 illustrates the unit pattern 1210 which directly charges acapacitor 1212, instead of parasitic capacitance.

Specifically, the unit pattern 1210 may directly charge the capacitor1212 coupled to a source follower with photocurrent generated from theTFT photodetector 1211.

In the embodiment of FIG. 12, the use of the capacitor 1212 may lead tolarger capacitance than parasitic capacitance. Further, the largecapacitance may be controlled to obtain a larger dynamic-range outputcharacteristic.

Photocurrent obtained by photo-electric conversion in the TFTphotodetector 1211 may be charged in the capacitor 1212 of an IVCcircuit inside a pixel due to turn-on of the selection transistor M1.

Further, the photocurrent charged in the capacitor 1212 may be convertedinto a voltage and output as IVC_OUT, which may be delivered in the formof a signal to a separate driving circuit such as CDS.

The transmitted signal may be reset by the selection transistor M1.

For example, when BUS RST (M2) is turned on in the turn-on state of theselection transistor M1, charges may be removed from the capacitor 1212,an entire column bus, and the TFT photodetector 1211 of the IVC circuitthrough a ground GND.

When the unit patterns 1110 and 1210 are used, a light source of adisplay may also be used as a light source of a touch sensor. Inaddition, both of a BLU of an LCD and a light emitting source of an OLEDmay be used. Further, it is possible to detect light in the wavelengthband of a near-infrared area which is longer than a maximum wavelength1150 nm detectable in general silicon.

With reference to FIGS. 13 and 14, the structure and operation of thetouch screen panel will be described in detail in specific embodiments.

FIG. 13 is a diagram illustrating a touch screen panel 1300 according toan embodiment of the disclosure.

According to an embodiment, the touch screen panel 1300 may include atouch panel 1320 with at least one unit pattern 1321 which detects lightreflected by a touch by using a TFT photodetector having an active layerformed of a-Si or poly-Si on an amorphous transparent material, and acontroller 1310 which scans the at least one unit pattern 1321 and readstouch coordinates as a result of the scanning.

More specifically, the touch panel 1320 may include a plurality of firstunit patterns arranged in rows and a plurality of second unit patternsarranged in columns.

For example, the first unit patterns may refer to sets of unit patternsgrouped in a row direction, for row-wise line scanning.

The second unit patterns may refer to sets of unit patterns grouped in acolumn direction, for column-wise line scanning.

Therefore, a unit pattern 1321 may be included in the first unitpatterns and the second unit patterns.

That is, the touch panel 1320 includes the plurality of first unitpatterns arranged in parallel to each other in a first direction (e.g.,X direction) and the plurality of second unit patterns arranged inparallel to each other in a second direction (e.g., Y direction) thatcrosses the first direction.

The controller 1310 may sequentially scan the row-wise first unitpatterns row by row by sequentially supplying a high-potential powervoltage to the first unit patterns arranged in the row direction on thetouch panel 1320.

Further, the controller 1310 may float the other row-wise unit patternsexcept for row-wise unit patterns to which the power voltage iscurrently applied.

In the floating state, a current path between the unit patterns and avoltage source is opened. Therefore, no external voltage is applied tothe unit patterns in the floating state. The controller 1310 may furtherinclude horizontal line control switches 1330 which supply ahigh-potential power voltage to the first unit patterns, respectively.Although the horizontal line control switches 1330 are shown as formedbetween the controller 1310 and the touch panel 1320 in FIG. 13, thoseskilled in the art will appreciate that the horizontal line controlswitches 1330 may be modified to be included in the controller 1310 orthe touch panel 1320.

The controller 1310 may scan the second unit patterns by sequentiallysupplying a power voltage to the column-wise second unit patterns afterthe row-wise first unit patterns are fully scanned line by line.

Similarly to the operation for the row-wise unit patterns, the othercolumn-wise unit patterns except for column-wise unit patterns chargedwith the high-potential power voltage may be floated.

The controller 1310 according to an embodiment of the disclosure mayfurther include vertical line control switches 1340 which supply ahigh-potential power voltage to the second unit patterns, respectively.

Referring to FIG. 13, upon occurrence of a touch in a first unit pattern1321 when a first horizontal line control switch and a first verticalline control switch are turned on, the capacitance of the first unitpattern 1321 may be changed.

When the unit pattern 1321 uses parasitic capacitance generated in themanner illustrated in FIG. 9, conversion to a voltage output may beperformed by the parasitic capacitance charged according to the touch.

When the additional capacitor 1012 is used as illustrated in FIG. 10, atouch may be sensed using capacitance larger than the parasiticcapacitance. In this case, a larger dynamic range output characteristicmay be obtained than in the case of using parasitic capacitance.

The controller 1310 may generate scanning control signals for drivingthe touch panel 1320.

Further, the controller 1310 may be coupled to the first unit patternsand the second unit patterns of the touch panel 1320, differentiallyamplify a voltage of initial capacitance of the unit patterns and avoltage of touch capacitance of the unit patterns, and convert thedifferential amplification result into digital data.

Further, the controller 1310 may determine a touch position based on thedifference between the initial capacitance and the touch capacitance bya touch recognition algorithm, and may output touch coordinate dataindicating the touch position.

FIG. 14 illustrates a touch screen panel according to another embodimentof the disclosure.

Referring to FIG. 14, a touch screen panel according to an embodiment ofthe disclosure includes a touch panel 1410, a driver 1420, a detector1430, a signal converter 1440, and a calculator 1450. The touch panel1410 may include first unit patterns arranged on a first axis (in an Xdirection) and second unit patterns arranged on a second axis (in a Ydirection).

The capacitance of a unit pattern 1421 at the intersection between afirst unit pattern and a second unit pattern may be changed. Thecapacitance change may be a change in mutual capacitance generated by adriving signal applied to the first unit pattern by the driver 1420. Thedriver 1420, the detector 1430, the signal converter 1440, and thecalculator 1450 may be collectively interpreted as a controller and maybe implemented into one integrated circuit (IC).

The driver 1420 may apply a predetermined driving signal to the firstunit patterns on the touch panel 1410. The driving signal may be asquare wave, sine wave, triangle wave, or the like having apredetermined period and amplitude, and may be sequentially applied toeach of the plurality of first unit patterns. While circuits forgenerating and applying a driving signal are shown as connected to therespective individual first unit patterns in FIG. 14, one driving signalgeneration circuit may be provided to apply a driving signal to each ofthe plurality of first unit patterns.

The detector 1430 may include an integration circuit for detecting achange in capacitance from a second unit pattern. The integrationcircuit may include at least one operational amplifier and a capacitorhaving a predetermined capacitance. An inverting input terminal of theoperational amplifier is coupled to the second unit pattern, converts acapacitance change into an analog signal such as a voltage signal, andoutputs the analog signal.

When a driving signal is sequentially applied to each of the pluralityof first unit patterns, changes in the capacitances of the plurality ofsecond unit patterns may be detected simultaneously. Accordingly, asmany integration circuits as the number of the second unit patterns maybe provided.

The signal converter 1440 generates a digital signal from an analogsignal generated by an integration circuit. For example, the signalconverter 440 may measure a time during which the analog signal outputin the form of a voltage from the detector 1430 reaches a predeterminedreference voltage level, and measure a variation of an analog signaloutput from a time-to-digital converter (TDC) which converts the time toa digital signal or the detector 1430 for a predetermined time. Further,the signal converter 1440 may include an analog-to-digital converter(ADC) circuit which converts the measurement to a digital signal.

The calculator 1450 may determine a touch input applied to the touchpanel 1410 using a digital signal. In an embodiment of the disclosure,the calculator 1450 may determine the number of touch inputs applied tothe touch panel 1410, the coordinates of the touch inputs, gestures, andthe like.

FIG. 15 is a block diagram illustrating a controller 1500 according toan embodiment of the disclosure.

Referring to FIG. 15, the controller 1500 according to an embodiment ofthe disclosure may include a first integration processor 1510, acomparator 1520, and a noise canceller 1530.

According to another embodiment of the disclosure, the controller 1500may further include a second integration processor 1540 and a driver1550.

In FIG. 15, a capacitor Cm corresponds to a capacitor charged withcapacitance that the controller 1500 wants to measure.

For example, the capacitance of the capacitor Cm may be interpreted asmutual capacitance generated between a plurality of electrodes includedin a capacitive touch screen.

The capacitor Cm may be assumed to be a node capacitor which is chargedor discharged by a change in mutual capacitance generated at theintersection between the plurality of electrodes.

The first integration processor 1510 may include a first capacitorcharged or discharged by the capacitor Cm.

The first capacitor may be coupled to the capacitor Cm by an integrationcircuit including an operational amplifier OP-AMP, and may be charged byreceiving charge from the capacitor Cm.

The first integration processor 1510 may output a voltage correspondingto the charge of the first capacitor. The output voltage of the firstintegration processor 1510 is input to the comparator 1520 and the noisecanceller 1530. The comparator 1520 may compare the level of the voltagesignal output from the first integration processor 1510 with a referencelevel, and transmit the comparison result to the noise canceller 1530.

The noise canceller 1530 may remove the influence of noise included inthe output voltage of the first integration processor 1510 according tothe result of comparing the output voltage level of the firstintegration processor 1510 with the reference level.

The output voltage of the first integration processor 1510 from whichthe influence of noise has been removed by the comparator 1520 and thenoise canceller 1530 is provided to the second integration processor1540. The overall configuration of the second integration processor 1540is similar to that of the first integration processor 1510. That is, thesecond integration processor 1540 may include a second capacitor chargedor discharged by an output voltage of the first integration processor1510, and generate an output signal determined by the amount of chargein the second capacitor.

When the controller 1500 according to the present embodiment is appliedto a capacitive touch screen, the output signal of the secondintegration processor 1540 may be input to an ADC and converted into adigital signal in the ADC. The digital signal converted by the ADC maybe used as sensing data based on which a calculator determines a touchinput.

FIG. 16 is a diagram 1600 illustrating a touch panel that processestouch recognition using an infrared (IR) light source.

The touch panel may include display pixels that emit light and a touchpanel that collects light. The touch panel may further include aprocessor that processes touch recognition along with positioning of abody according to the light collected by the touch panel

In the present embodiment, the disclosure will be described in detail,centering on a touch panel which substantially serve as a touch paneland a transparent material.

A touch panel and a display pixel may be arranged side by side on thesame layer or may overlap with each other. Since the touch panel isformed on a transparent material, stacking the touch panel on thedisplay pixel does not make a big visual difference.

A touch panel and a display pixel may be included together in a unitpixel to form one pixel of the touch panel. The touch panel may includea TFT photodetector having an active layer formed of a-Si or poly-Si onan amorphous transparent material, and collect light reflected from abody located on the transparent material.

In the case of an IR-based optical touch screen, use of a TFTphotodetector-based image sensor very sensitive to IR rays in the mannerillustrated in FIG. 16 enables simultaneous recognition of thefingerprint and vein of a finger.

When the finger touches IR light penetrating through glass 1620, the IRlight reflected from the finger is incident on the cells of TFTphotodetectors distributed in a corresponding area, and signals from thecells are acquired as an image based on which the fingerprint may berecognized. Because the vein of the finger may also be acquired at thesame time by external light or the reflected IR light, a very high levelof security may be guaranteed.

Particularly, the disclosure is characterized in that a unit cellcapable of securing an image is distributed in each pixel on a wholesurface of the display, so that a fingerprint and a vein may berecognized from the whole surface of the display, instead of a specificposition on the display. That is, the problem of additionally disposinga fingerprint recognition sensor and using it overlapped with thedisplay panel may be simply overcome, and the touch screen function mayalso be used together. Therefore, a touch panel which is thinner andcheaper than a conventional touch panel may be fabricated.

A TFT photodetector according to an embodiment of the disclosure isformed on the glass 1620 being a transparent material, such as anamorphous glass substrate or a flexible substrate.

For better understanding, the disclosure will be described in thecontext of the amorphous glass 1620 as a transparent material.

The TFT photodetector includes, on the glass 1620, the gate 150 formedof a-Si or poly-Si, the insulating oxide film 140 capable of controllingtunneling of photo-excited charges, the drain 110, the source 120, andthe active layer 130 in which a current channel is to be formed betweenthe source 120 and the drain 110. Although the drain 110, the source120, the active layer 130, and the gate 150 are formed of a-Si orpoly-Si, they may be formed of any other material, as far as theconductive property of the material is controllable by tunneling or anelectric field.

An area on which light reflected from the body is incident is confinedto the gate 150 serving as the light receiver and the active layer 130with the insulating oxide film 140 interposed between the active layer130 and the gate 150. For this purpose, the metal protection layer 160may be formed on a boundary surface of the transparent substrate, exceptfor the area between the transparent substrate and the active layer 130,to shield unnecessary light introduced into the TFT photodetector 100through the glass 1620. The metal shielding layer 170 may be formed inthe remaining area except for the gate 150 in the upper part of the TFTphotodetector. The shielding layer 170 may be formed by a silicide andmetal process. The TFT photodetector limits an area on which light isincident to the gate 150 serving as the light receiver by means of theshielding layer 170, thereby maximizing the photoelectric conversion inthe gate 150.

When IR light is irradiated from an IR light source 1610, the IR lightis reflected back from a body 1630 and then used for touch recognition.

The IR light source 1610 may irradiate IR light from one side of theglass 1620 being a transparent material to cause diffused reflection inthe glass 1620.

The touch panel may collect IR light which has been diffusedly reflectedfrom the body contacting the glass 1620.

The processor may process touch recognition together with positioning ofthe body 1630 from the light which has been generated by the IR lightsource 1610 and then collected.

For example, the processor may identify information about at least oneof a vein, a fingerprint, or a face based on the light reflected fromthe body 1630, and process touch recognition by comparing the identifiedinformation with pre-stored information.

The body 1630 is a part from which uniquely identifiable biometricinformation may be acquired, and may be interpreted as the tip of afinger, a palm, or the like from which a fingerprint may be acquired.

Further, the processor may process touch recognition along withpositioning of the body 1630 according to light reflected from the body1630.

With reference to FIG. 16, the embodiment in which after the IR lightsource irradiates IR light from one side of a touch panel, the IR lightis reflected from the body 1630 during diffused reflection in the glass1620 and collected by the TFT photodetector, and touch recognition isprocessed based on the reflected light by the processor has beendescribed above.

FIG. 17 illustrates an embodiment 1700 of using a backlight light sourceinstead of an IR light source.

In FIG. 17, a touch panel that processes touch recognition using abacklight as a light source is illustrated.

A backlight light source 1710 may be used as a light source for the TFTphotodetector.

The backlight light source 1710 may irradiate backlights in atransmission direction of the transparent material through a spacebetween adjacent TFT photodetectors.

As illustrated in FIG. 17, the metal protection layer 160 for blockinglight is formed on a boundary surface of glass 1720 being a transparentmaterial except for an area between the glass 1720 and the active layer130, to block the introduction of unnecessary light into the TFTphotodetector through the glass 1720.

The touch panel may collect light which has passed through the glass1720 and then reflected from the body, and the processor may processtouch recognition together with positioning of the body from the lightwhich has been generated by the backlight light source and thencollected. Particularly, the processor may process touch recognitiontogether with positioning of the body from light which has beengenerated by the backlight light source, reflected from the bodycontacting the transparent material, and then collected.

For example, the processor may identify information about at least oneof a vein, a fingerprint, or a face based on the light reflected fromthe body, and process touch recognition by comparing the identifiedinformation with pre-stored information, for the display panel.

Use of the backlight light source 1710 as a light source for the TFTphotodetector enables simultaneous recognition of the fingerprint andvein of a finger. When the finger touches backlight penetrating throughthe glass 1720, the backlight reflected from the finger is incident onthe cells of TFT photodetectors distributed in a corresponding area, andsignals from the cells are acquired as an image based on which thefingerprint may be recognized. Because the vein of the finger may alsobe acquired at the same time by external light or backlight, a very highlevel of security may be guaranteed.

Further, the disclosure is characterized in that a unit cell capable ofsecuring an image is distributed in each pixel on a whole surface of thedisplay, so that a fingerprint and a vein may be recognized from thewhole surface of the display, instead of a specific position on thedisplay. That is, the problem of additionally disposing a fingerprintrecognition sensor and using it overlapped with the touch panel may besimply overcome, and the touch screen function may also be usedtogether. Therefore, a touch panel which is thinner and cheaper than aconventional touch panel may be fabricated.

As a result, according to the disclosure, a highly sensitive touch panelmay be implemented on a glass substrate or a flexible substrate such asa polyimide film, used as a touch panel by the TFT fabricationtechnology.

Besides, since a light emitting device or a BLU of the display is usedas a light source for a touch panel, touch sensing may be processedwithout using a separate light emitter required for the touch panelaccording to the disclosure.

As is apparent from the foregoing description of various embodiments ofthe disclosure, a high-sensitivity touch panel may be implemented on aglass substrate or a flexible substrate such as a polyimide film, whichis used as a touch panel, by a TFT fabrication technology.

According to an embodiment of the disclosure, touch recognition may beprocessed fast and accurately using a touch screen panel having adisplay pixel and a touch panel integrated thereon.

According to an embodiment of the disclosure, touch sensing may beprocessed without the need for separately providing a light emitter fora touch panel, by using a light emitting device or BLU of a display as alight source for the touch panel.

According to an embodiment of the disclosure, a transparent touch panelcapable of displaying and touch sensing may be implemented by verticallystacking a display panel and a touch panel or arranging the displaypanel and the touch panel on the same panel.

According to an embodiment of the disclosure, a switching TFT fordisplay and a driving TFT for image sensing may be fabricated in asingle process by arranging a display panel and a touch panel on thesame panel.

According to an embodiment of the disclosure, a light source for adisplay may also be used as a light source for a touch panel.

According to an embodiment of the disclosure, both of a BLU of an LCDand a light emitting source of an OLED may be used.

According to an embodiment of the disclosure, it is possible to detectlight in the wavelength band of a near-IR area longer than a maximumdetectable wavelength, 1150 nms in general silicon.

The above description is merely illustrative of the technical idea ofthe disclosure, and those skilled in the art may make variousmodifications and changes without departing from the essential featuresof the disclosure. In addition, the embodiments disclosed herein areintended to describe the disclosure, not limiting the technical spiritof the disclosure, and the scope of the technical idea of the disclosureis not limited by these embodiments. Therefore, the protection scope ofthe disclosure should be interpreted by the appended claims, and alltechnical ideas within their equivalency should be construed as beingembraced in the scope of the disclosure.

What is claimed is:
 1. A touch screen panel using a thin film transistor(TFT) photodetector, the touch screen panel comprising: a touch panelincluding a plurality of unit patterns for sensing light reflected by atouch by using a TFT photodetector including an active layer formed ofamorphous silicon or polycrystalline silicon on an amorphous transparentmaterial; and a controller configured to scan the plurality of unitpatterns and read touch coordinates as a result of the scanning, whereinthe TFT photodetector is formed in a structure in which when light isincident, electrons migrate into an N-type gate by tunneling from aP-type active layer to an oxide film, among charges of two PN areasexcited with the oxide film in between, the electron migration changes athreshold voltage of a current channel between a source and a drain incorrespondence with a change in a total amount of charge in the gate,photocurrent proportional to the intensity of the incident light flowsin the active layer, and a voltage output is generated from the flowingphotocurrent.
 2. The touch screen panel according to claim 1, whereinthe plurality of unit patterns comprise a plurality of first unitpatterns which are arranged in parallel with each other in a firstdirection, and a plurality of second unit patterns which are arranged inparallel with each other in a second direction crossing the firstdirection, insulated from the first unit patterns.
 3. The touch screenpanel according to claim 2, wherein the controller is configured to:scan each of the first unit patterns by supplying a first voltage to theplurality of first unit patterns in line by line manner; scan all of theplurality of second unit patterns by sequentially supplying the firstvoltage to the plurality of second unit patterns according to a firstscanning control signal, each time each of the plurality of first unitpatterns is scanned; and connect to the first and second unit patternsof the touch panel and detect a touch recognition signal indicatingwhether a touch has occurred, and a touch position by comparing avoltage of initial capacitance of each of the first and second unitpatterns with a voltage of current capacitance of the unit pattern, eachtime the first voltage is supplied to the plurality of first unitpatterns and the plurality of second unit patterns by a driving circuit.4. The touch screen panel according to claim 2, wherein the controllercomprises a first driving circuit configured to scan the first unitpatterns by supplying the first voltage to the first unit patterns, anda second driving circuit configured to scan the second unit patterns bysupplying the first voltage to the second unit patterns.
 5. The touchscreen panel according to claim 4, wherein the first driving circuitcomprises a plurality of first control switches configured torespectively supply the first voltage to the plurality of first unitpatterns in response to a first scanning control signal and a secondscanning signal from the controller, and a plurality of second controlswitches configured to respectively supply the first voltage to theplurality of second unit patterns in response to the first scanningcontrol signal and the second scanning signal from the controller. 6.The touch screen panel according to claim 1, wherein the controllercomprises: a first integration processor including a first capacitorcharged by a capacitance variation in the first unit patterns; acomparator configured to compare a level of an output signal of thefirst integration processor with a predetermined reference level; and anoise canceller including a plurality of switches operating according toan output of the comparator, wherein when the level of the output signalof the first integration processor is higher than the reference level,the comparator controls each of the plurality of switches to dischargethe first capacitor.
 7. The touch screen panel according to claim 6,wherein the controller further comprises: a second integration processorincluding a second capacitor charged by the charged first capacitor; anda calculator configured to determine a touch input from an output signalof the second integration processor.
 8. The touch screen panel accordingto claim 7, wherein the noise canceller comprises a first switchconnected to a ground and a second switch connected to an input node ofthe second integration processor, and wherein when the level of theoutput signal of the first integration processor is higher than thereference level, the comparator is configured to turn off the secondswitch and turn on the first switch.
 9. The touch screen panel accordingto claim 6, wherein the comparator comprises: a first comparison circuitconfigured to compare the level of the output signal of the firstintegration processor with a first reference level; and a secondcomparison circuit configured to compare the level of the output signalof the first integration processor with a second reference level, andwherein when the level of the output signal of the first integrationprocessor is higher than the first reference level or lower than thesecond reference level, the comparator operates each of the plurality ofswitches to discharge the first capacitor.
 10. The touch screen panelaccording to claim 1, wherein the touch panel further comprises aninfrared (IR) light source configured to cause diffused reflection onthe transparent material by irradiating IR light from one side of thetransparent material, and wherein the plurality of unit patterns collectthe IR light diffusedly reflected from a body contacting the transparentmaterial, and the controller processes touch recognition along withpositioning of the body by the light generated from the IR light sourceand then collected.
 11. The touch screen panel according to claim 1,wherein the touch panel further comprises a backlight light sourceconfigured to irradiate backlight in a transmission direction of thetransparent material through a space between adjacent TFTphotodetectors, and wherein the plurality of unit patterns collect thebacklight passed through the transparent material and then reflectedback from the body, and the controller processes touch recognition alongwith the positioning of the body by the light generated from thebacklight light source and then collected.
 12. The touch screen panelaccording to claim 1, wherein the TFT photodetector is electricallycoupled to at least one transistor and the at least one transistor isconfigured to generate a voltage output from photocurrent generated inthe active layer.
 13. The touch screen panel according to claim 1,wherein the active layer includes a material having a conductiveproperty controllable by tunneling or an electric field.
 14. The touchscreen panel according to claim 1, wherein the TFT photodetector useslight generated from a display panel as a light source for the pluralityof unit patterns.
 15. A touch screen panel using a thin film transistor(TFT) photodetector, the touch screen panel comprising: a touch panelincluding a plurality of unit patterns for sensing light reflected by atouch by using a TFT photodetector including an active layer formed ofamorphous silicon or polycrystalline silicon on an amorphous transparentmaterial; and a controller configured to scan the plurality of unitpatterns and read touch coordinates as a result of the scanning, whereinthe TFT photodetector comprises: an amorphous transparent substrateincluding the transparent material; a source formed of amorphous siliconor polycrystalline silicon on the transparent substrate; a drain formedof amorphous silicon or polycrystalline silicon, opposite to the sourceon the transparent substrate; and the active layer formed between thesource and the drain and including a current channel formed between thesource and the drain.
 16. The touch screen panel according to claim 15,wherein the TFT photodetector further comprises: an insulating oxidefilm formed on the source, the drain, and the active layer; and a lightreceiver formed on the insulating oxide film, configured to absorblight, and insulated from the active layer by the insulating oxide film.17. The touch screen panel according to claim 16, wherein in the TFTphotodetector, when light is incident on the light receiver, electronsmigrate by tunneling through the insulating oxide film between the lightreceiver and the active layer excited with the insulating oxide film inbetween, the electron migration changes an amount of charge in the lightreceiver, the changed amount of charge changes a threshold voltage ofthe current channel, and thus photocurrent flows in the current channel.